Hermetically Sealed

Closed securely. Thus we say, “My lips are hermetically
sealed,” meaning so as not to utter a word of what has been imparted.
The French say close-fitting doors and windows “shut hermetically.”
When chemists want to preserve anything from the air, they heat the
neck of the vessel till it is soft, and then twist it till the aperture
is closed up. This is called sealing the vessel hermetically, or like a
chemist. (From Hermës, called Trismegistus, or thrice-great, the
supposed inventor of chemistry.)